Calculations involving gas volumes
3 marks · EasyHydrogen peroxide decomposes to form water and oxygen gas as shown:
Write the stoichiometric ratio between hydrogen peroxide and oxygen in the equation above.
Calculate the volume, in dm³, of oxygen gas produced at rtp from complete decomposition of 0.50 mol of hydrogen peroxide.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) 2 : 1
(b) 0.25 × 24 = 6 dm³
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correct ratio 2 : 1 (allow 2H2O2 : 1O2)
M1 (b) · 1 mark · Correctly determines moles of O2 from H2O2 (0.50 mol H2O2 makes 0.25 mol O2) or writes correct relationship.
A1 (b) · 1 mark · Correctly calculates volume: 0.25 × 24 = 6 dm³ (follow-through)
Worked solution
a) From the equation: 2 moles of H₂O₂ produce 1 mole of O₂, so the ratio is 2 : 1.
b) 0.50 mol H₂O₂ will produce 0.25 mol O₂ (half as many moles).